Sylvie Nadeau

Analysis of the clinical factors determining natural and maximal gait speeds in adults with a stroke.

The objective of this study was to identify the most important clinical variables determining gait speed in persons with stroke. Sixteen chronic stroke subjects (mean age, 47.9 (+/-15.6) yr; mean time post-stroke, 43.9 (+/-36.5) mo) able to walk independently without a brace participated in the study. The impairments in motor function, sensation of the paretic lower limb, and balance were evaluated with the Fugl-Meyer Assessment. A spasticity index was used to assess the muscle tone of the plantarflexors. The maximal strengths in plantarflexion and hip flexion were measured with a Biodex dynamometric system. Cinematography and foot-contact data collected on the paretic side were used to determine the comfortable and maximal gait speeds. The level of association between gait speeds and the clinical variables were first examined with Pearsons correlation coefficients and, then, with multiple linear regression analyses using the stepwise method. Results revealed that the motor function of the lower limb, balance, and hip flexion strength were significantly related to comfortable and maximal gait speeds (0.5 < r < 0.88; P < 0.05). For the comfortable gait speed, the regression analysis selected only the hip flexor strength as a significant variable (R2 = 0.69). For maximal gait speed, the variables retained were hip flexor strength, sensation at the lower limb, and plantarflexor strength (R2 = 0.85). The present results suggest that strength and sensation at the lower limb are important factors to consider in determining the gait capacity of chronic stroke subjects.

Task-oriented intervention in chronic stroke : Changes in clinical and laboratory measures of balance and mobility

Leroux A, Pinet H, Nadeau S: Task-oriented intervention in chronic stroke: Changes in clinical and laboratory measures of balance and mobility. Am J Phys Med Rehabil 2006;85:820–830. Objective:The objective of this study was to evaluate whether, after a task-oriented exercise program, the changes in clinical measures of balance and mobility were paralleled by changes in biomechanical parameters in subjects with chronic stroke. Design:Ten stroke subjects took part in an 8-wk exercise program aimed at improving balance and mobility through various functional tasks. Subjects were evaluated before and after the exercise intervention. Clinical measures included the Berg Balance Scale and the Timed-Up-and-Go and laboratory measures included ground reaction forces and center of pressure displacement during four functional tasks. Results:Stroke subjects showed significant improvements (P < 0.05) in the clinical measures after completing the exercise program. Significant improvements (P < 0.05) were also found in postural steadiness during tandem stance and stool touch and in force production through the paretic lower limb during sit-to-stand. This last result was strongly correlated (r = −0.93) with the improvements on the Timed-Up-and-Go after exercise intervention. In contrast, the increase in postural steadiness was poorly correlated with the improvements on the Berg Balance Scale. Conclusions:A task-oriented exercise program might improve both clinical and laboratory measures of balance and mobility in stroke subjects. However, several correlations between the changes in clinical and laboratory measures after exercise intervention were generally weak, indicating that these outcome measures assessed different components of improvements.

INTERACTIONS BETWEEN FOOT PLACEMENT, TRUNK FRONTAL POSITION, WEIGHT-BEARING AND KNEE MOMENT ASYMMETRY AT SEAT-OFF DURING RISING FROM A CHAIR IN HEALTHY CONTROLS AND PERSONS WITH HEMIPARESIS

OBJECTIVE To assess the interaction of foot placement, trunk frontal position, weight-bearing and knee moment asymmetry at seat-off when rising from a chair. DESIGN Cross-sectional study. SUBJECTS Seventeen subjects with hemiparesis and 15 healthy controls. METHODS Trunk position, weight-bearing and knee moment asymmetry were quantified by kinetic and kinematic analysis when the subjects rose from a chair using 3 different foot placements: spontaneous, symmetrical and asymmetrical. Asymmetry was defined by the ratio between sides. RESULTS In the healthy controls, the spontaneous and symmetrical foot placements were associated with an almost vertical trunk position and a symmetrical weight-bearing and knee moment. The asymmetrical foot placement resulted in a trunk displacement towards the foot placed behind, with more weight-bearing and higher moment on this side. The opposite was observed in the hemiparetic participants where the spontaneous and symmetrical foot conditions determined a trunk position and an asymmetry bias towards the unaffected side. Placing the affected foot behind the other reduced the asymmetrical behaviour. CONCLUSION Changes in weight-bearing are partly associated with the frontal trunk position, and foot placement manipulations can be used to modify weight-bearing distribution. Inference on weight-bearing is possible by observing the trunk position during the sit-to-stand task in persons with hemiparesis.

Proposal of a risk-factor-based analytical approach for integrating occupational health and safety into project risk evaluation.

Excluding occupational health and safety (OHS) from project management is no longer acceptable. Numerous industrial accidents have exposed the ineffectiveness of conventional risk evaluation methods as well as negligence of risk factors having major impact on the health and safety of workers and nearby residents. Lack of reliable and complete evaluations from the beginning of a project generates bad decisions that could end up threatening the very existence of an organization. This article supports a systematic approach to the evaluation of OHS risks and proposes a new procedure based on the number of risk factors identified and their relative significance. A new concept called risk factor concentration along with weighting of risk factor categories as contributors to undesirable events are used in the analytical hierarchy process multi-criteria comparison model with Expert Choice(©) software. A case study is used to illustrate the various steps of the risk evaluation approach and the quick and simple integration of OHS at an early stage of a project. The approach allows continual reassessment of criteria over the course of the project or when new data are acquired. It was thus possible to differentiate the OHS risks from the risk of drop in quality in the case of the factory expansion project.

Biomechanical analysis of a posterior transfer maneuver on a level surface in individuals with high and low-level spinal cord injuries

OBJECTIVE The purpose of this study was to determine the movement patterns and the muscular demand during a posterior transfer maneuver on a level surface in individuals with spinal cord injuries. DESIGN Six participants with high-level spinal cord injury (C7 to T6) were compared to five participants with low-level spinal cord injury (T11 to L2) with partial or complete control of abdominal musculature. BACKGROUND Developing an optimal level of independence for transfer activities figures among the rehabilitation goals of individuals with spinal cord injury. There has been no biomechanical study which specifically describes the posterior transfer maneuver. METHODS Tridimensional kinematics at the elbow, shoulder, head and trunk, as well as surface electromyographic data of the biceps, triceps, anterior deltoid, posterior deltoid, pectoralis major, latissimus dorsi, trapezius and rectus abdominus muscles were recorded during the posterior transfer. To quantify the muscular demand, the electromyographic data were amplitude normalized to the peak value obtained from maximum voluntary contractions. The transfer was divided into pre-lift, lift, and post-lift phases for analysis. RESULTS The duration of the lift phase was significantly shorter (P<0.05) for the high-level spinal cord injury (1.24; SD, 0.37 s) when compared to the low-level spinal cord injury (1.74; SD, 0.39 s). The patterns and magnitudes of the angular displacements were found similar between groups (P values: 0.45-0.98). However, the high-level spinal cord injury initiated the task from a forward flexed posture, whereas the low-level spinal cord injury adopted an almost upright alignment of the trunk. Higher muscular demands were calculated for all muscles among high-level spinal cord injury participants during the transfer when compared to the low-level spinal cord injury. However, only the anterior deltoid (high level=92.4%; low level=34.2%) and the pectoralis major (high level=109.8%; low level=25.6%) reached statistical significance during the lift phase.Conclusions. Participants with high-level spinal cord injury presented different movement characteristics and higher muscular demands during the posterior transfer than low-level spinal cord injury ones. This is probably to compensate for the additional trunk and upper limb musculature impairment. RELEVANCE The findings of this study may help to develop guidelines of specific strengthening programs for the thoracohumeral, scapulothoracic and shoulder muscles designed to restore optimal transfer capacity in individuals with spinal cord injury. Furthermore, innovative rehabilitation programs targeting the ability to control the trunk could be beneficial for these individuals.

Pelvic stabilization and semisitting position increase the specificity of back exercises.

PURPOSE To examine the effect of pelvic stabilization and two lower-limb configurations on the EMG activity of back and hip extensor muscles during a dynamic back extension exercise on a machine and to compare them between sexes. METHODS Twenty-two healthy volunteers (11 men and 11 women) performed five trunk flexion-extension cycles at 40% of their maximal voluntary contraction (MVC) in a machine designed for back exercise. Two different positions were used: 1) seated position (seat horizontal, knees at 90 degrees ) and 2) semisitting position (seat slightly tilted forward at 15 degrees , knees at 45 degrees of flexion). In each position, three pelvic stabilization conditions were tested: 1) unrestrained (control condition), 2) partially restrained (posteriorly), and 3) totally restrained (posteriorly and anteriorly). EMG signals were recorded bilaterally with 12 pairs of electrodes placed on back muscles as well as on the gluteus maximus and biceps femoris. The muscular activation level, that is, the percentage of EMG amplitude relative to the maximal EMG obtained from MVC, was used to asses the relative contribution of each muscle group across exercises. RESULTS In both sexes, two main results were found: 1) pelvic stabilization (partially and totally restrained) significantly (P < 0.05) increased the activity of all back muscles (average of 12%) and 2) semisitting position significantly decreased (range = 8-27%) the activity of two hip extensors compared with the seated position. Sex differences were also observed relative to the activity of some back muscles as well as the biceps femoris. CONCLUSIONS Combining pelvic stabilization and semisitting position in back exercise machines might be a useful way to localize the effects of endurance training at the back muscles and this in both the sexes.

COMPARISON Of MULTIDIRECTIONAL SEATED POSTURAL STAbILITy bETwEEN INDIvIDUALS wITh SPINAL CORD INJURy AND AbLE­bODIED INDIvIDUALS

OBJECTIVES To compare multidirectional seated postural stability between individuals with spinal cord injury and able-bodied- individuals and to evaluate the impact of abdominal and low back muscle paralysis on multidirectional seated stability. DESIGN Case-control study. PARTICIPANTS Fifteen individuals with complete or incomplete spinal cord injury affecting various vertebral levels participated in this study and were gender-matched with 15 able-bodied individuals. METHODS Participants were instructed to lean as far as possible in 8 directions, set apart by 45° intervals, while seated on an instrumented chair with their feet placed on force plates. Eight direction-specific stability indices and a global stability index were calculated. RESULTS The global stability index and all direction-specific indices, except in the anterior and posterior directions, were lower in individuals with spinal cord injury than in able-bodied individuals. However, the individuals with spinal cord injury who had partial or full control of their abdominal and lower trunk muscles obtained a similar global stability index and similar direction-specific indices compared to the able-bodied individuals. CONCLUSION Multidirectional seated postural stability is reduced in individuals with SCI who have paralysis of the abdominal and lower back muscles in comparison to able-bodied individuals.

Specificity of a back muscle roman chair exercise in healthy and back pain subjects.

PURPOSE Roman chair exercises are popular for improving back muscle endurance but do not specifically target back muscles. This study aimed to determine whether an adaptation of the Roman chair exercise would induce more fatigue in back muscles than in hip extensors. METHODS For this study, 16 healthy subjects and 18 patients with nonspecific chronic low back pain performed trunk flexion-extension cycles until exhaustion in a Roman chair with hips flexed at 40°. Surface EMG signals were recorded bilaterally on four back muscles and two hip extensors (gluteus maximus and biceps femoris). Motion analysis of the trunk segments (pelvis, lumbar, and thoracic spines) was also carried out. RESULTS In both groups, EMG revealed clear evidence of muscle fatigue for the gluteus maximus, less clear evidence of fatigue for the lower back muscles, and motor unit recruitment (without fatigue) for the upper back muscles and biceps femoris. A change of muscle activation pattern was emphasized throughout the exercise bout, with some lower back muscles showing an increase followed by a decrease or leveling off of activation and with upper back muscles showing an increased activation at the end. Kinematic analyses revealed a progressive decrease (11°) in the lumbar range of motion (ROM) and a progressive increase in hip (2°) and thoracic (7°) ROM during the exercise bout. CONCLUSIONS Roman chairs allow more freedom to change the kinematics of the spine during the exercise (less lumbar and more thoracic motion) to delay lower back muscle fatigue by sharing the load between the lower and upper back muscles. Even with adaptations to reduce hip extensors fatigue, this may make this exercise not as specific as wanted for fatiguing lower back muscles.

EFFECT OF PELVIC STABILIZATION AND HIP POSITION ON TRUNK EXTENSOR ACTIVITY DURING BACK EXTENSION EXERCISES ON A ROMAN CHAIR

OBJECTIVE To assess the effect of pelvic stabilization and hip position on the electromyographic activity of trunk extensors during Roman chair exercise. A secondary objective was to compare genders. DESIGN Repeated measures. SUBJECTS Eleven men and 11 women volunteers. METHODS Five trunk flexion-extension cycles for 3 Roman chair conditions: (i) pelvis unrestrained; (ii) pelvis restrained; and (iii) hip at 40 degrees flexion. Electromyographic signals were recorded on the back muscles, as well as on the gluteus maximus and biceps femoris. The percentage of electromyographic amplitude relative to the maximal activity was used to assess the level of muscular activation of each muscle group across the exercises. RESULTS For both genders, the Roman chair conditions did not influence the activity of the back and gluteus muscles. The hip-at-40 degrees-flexion condition significantly reduced the activity of the biceps femoris (average of 4-18%) relative to the other 2 conditions. Gender differences were observed on the activity of the biceps femoris in all Roman chair conditions. CONCLUSION The hip-at-40 degrees-flexion condition would allow the Roman chair exercise to train the targeted back muscles more specifically by overloading them over a longer duration in order to induce physiological changes.

A method to evaluate contractures effects during the gait of children with Duchenne dystrophy.

Joint contractures are the second major impairment affecting the locomotor system of children with Duchenne muscular dystrophy (DMD). While the negative influence of joint contractures has been documented, the passive moments produced by joint contractures could benefit the gait of patients with muscle weakness. We describe a biomechanical model that quantifies the mechanical contribution of ankle and hip flexion contractures to the gait of DMD children. Kinematic and kinetic parameters were measured under the same experimental conditions during the gait and passive resistance assessment of two subjects: one healthy child as a control, and one child with DMD. The child with DMD had a plantar flexion contracture and a greater ankle stiffness coefficient than the control child. During gait, the contribution of the ankle passive moment to the net moment was more important for the child with DMD than for the control child. At the hip, passive joint moments and passive moment contribution were more important for the control child but this was not related to the presence of hip flexion contrac-ture. These preliminary results suggest the model might be used to evaluate contractures effect on a larger cohort of subjects.